#34992 closed Bug (fixed)
MariaDB does not support functional group by dependencies
Reported by: | Matthew Somerville | Owned by: | Nathaniel Conroy |
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Component: | Database layer (models, ORM) | Version: | 4.2 |
Severity: | Release blocker | Keywords: | |
Cc: | Triage Stage: | Ready for checkin | |
Has patch: | yes | Needs documentation: | no |
Needs tests: | no | Patch needs improvement: | no |
Easy pickings: | no | UI/UX: | no |
Description
Requested to be opened from comment 11 on #34978. If you're using MariaDB with ONLY_FULL_GROUP_BY turned on, all queries that end up using a GROUP BY
fail. Given a model such as:
class Author(models.Model): pass class Play(models.Model): title = models.CharField(max_length=100) authors = models.ManyToManyField(Author)
Then list(Play.objects.annotate(Count('authors')))
generates the SQL:
SELECT app_play.id, app_play.title, COUNT(app_play_authors.author_id) AS authors__count FROM app_play LEFT OUTER JOIN app_play_authors ON (app_play.id = app_play_authors.play_id) GROUP BY app_play.id ORDER BY NULL
Which errors with django.db.utils.OperationalError: (1055, "'mariadbtest.app_play.title' isn't in GROUP BY")
Unlike MySQL since 5.7.5 (release notes: "MySQL now recognizes when a nonaggregated selected column is functionally dependent on (uniquely determined by) GROUP BY columns."), MariaDB does not support this feature. But Django 4.2 assumes both MySQL and MariaDB support it.
Simon's comment on #34978 said: "The solution will likely be to turn off the allows_group_by_selected_pks feature on MariaDB when ONLY_FULL_GROUP_BY mode is turned on. Note that the allows_group_by_selected_pks feature is different from the allows_group_by_pk feature removed in 041551d716b69ee7c81199eee86a2d10a72e15ab."
Change History (9)
comment:1 by , 11 months ago
Triage Stage: | Unreviewed → Accepted |
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comment:2 by , 11 months ago
Owner: | changed from | to
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Status: | new → assigned |
comment:3 by , 10 months ago
I think I understand the problem here, and I was able to test a simple solution locally.
However, this is my first ticket, so it may be a few days before I have a patch ready. I need to get more acquainted with the tests and the general workflow.
comment:4 by , 10 months ago
Has patch: | set |
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comment:6 by , 10 months ago
Triage Stage: | Accepted → Ready for checkin |
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Thanks for creating this Matthew 🏆